Introduction
Cervical transforaminal epidural steroid injections have been used routinely to treat patients with cervical radiculopathy. There has been a growing concern about their safety due to a paucity of morbidity and mortality data. Furthermore, although many theories have been postulated in regard to the mechanism of injury, there is a lack of clear understanding of the causes of serious central nervous system injuries associated with this type of injection.
Intra-arterial Injection in the Rat Brain: Evaluation of Steroids Used for Transforaminal Epidurals
Dawley JD, Moeller-Bertram T, Wallace MS, Patel PM
Spine. 2009;34:1638-1643
Summary
Dr. Dawley and colleagues sought to affirm the possibility that intra-arterial injection of commonly used corticosteroids could lead to central nervous system injury during a transforaminal epidural steroid injection. The team conducted the in vivo study with rodent models that were evaluated over a 3-day period.
After the rodents were placed under general anesthesia with mechanical ventilator support, they inserted a catheter into the external carotid artery of each rodent and advanced it into the internal carotid artery. The investigators then proceeded to inject 1 of 5 different solutions: (1) methylprednisolone acetate (Depo-Medrol®; 20x dilution of 40 mg/mL); (2) methylprednisolone sodium succinate (Solu-Medrol®); (3) methylprednisolone acetate carrier, obtained via centrifugation of methylprednisolone acetate solution; (4) dexamethasone (Decadron®); or (5) normal saline.
Evaluation was performed preoperatively with neurologic behavioral testing and then postoperatively with repeat neurologic testing, as well as posthumous gross and histologic examination of rodent brain tissue on postoperative day 3. Baseline neurologic testing was not available in this study.
Gross postmortem inspection of the rodent brains from each group showed gross cortical lesions in rats who received methylprednisolone acetate and methylprednisolone sodium succinate injections, but not in the control group. On histologic evaluation, hemorrhagic lesions were noted in 8 of 11 rodents in the methylprednisolone acetate (20x dilution) group, 7 of 8 in the methylprednisolone sodium succinate group, and 3 of 6 in the methylprednisolone acetate carrier group. Ischemic lesions and necrosis were also seen in these groups. The dexamethasone and saline groups showed no significant abnormalities on neurologic evaluation, gross anatomic examination, histologic assessment, or Evan's blue dye evaluation.
Viewpoint
The results of this study are consistent with other recent studies on the potential of particulate corticosteroids that have been injected intra-arterially and have caused neurologic injuries. Similar results were seen in another recent study that compared particulate steroid with nonparticulate steroids in porcine models in which steroids were injected directly into the vertebral artery under fluoroscopic guidance.
Current evidence appears to support the use of dexamethasone, a nonparticulate steroid, with cervical epidural steroid injections to potentially reduce the risk for neurologic injury. Patient safety should be of utmost concern, and every precaution should always be taken during such procedures.
The main limitations of this study included small sample size and the use of a methylprednisolone acetate carrier isolated via centrifugation, rather than a pure methylprednisolone acetate carrier sample.
Abstract